HEART-ATTACK.1
Heart Attack

A heart attack (myocardial infarction) occurs when a coronary artery is blocked by plaque or a blood clot. When this happens, the heart muscle beyond the blockage doesn’t receive enough oxygen. That part of the heart muscle begins to die. This damage cannot be reversed. Though many people survive heart attacks, a heart attack can be deadly.

Blood Flow

Oxygen-poor blood (blue arrows) is pumped to the lungs. Oxygen-rich blood (red arrows) is pumped to the rest of the body.

How the Heart Pumps Blood

The heart is a system of chambers and valves that keep blood moving in the correct direction. The heart muscle squeezes (beats) to move blood in and out of the heart’s four chambers. (These chambers are called ventricles and atria.) Four valves open and close to keep blood moving in the proper direction through the heart.

Valves Direct Blood Through the Heart

With each heartbeat, valves open and close. This moves blood in the correct

  • Oxygen-poor blood is pumped from the right atrium through the tricuspid valve into the right ventricle. It is then pumped through the pulmonic valve to the blood vessel that leads to the lungs. There, it picks up oxygen and returns to the heart through the pulmonary veins.
  • Oxygen-rich blood is pumped from the left atrium through the mitral valve into the left ventricle. It is then pumped through the aortic valve to the aorta, so it can travel to the rest of the body.

direction.